1. Field of the Invention
The present invention relates to a resinous composition composed of a thermoplastic resin and a saponified product of ethylene-vinyl acetate copolymer, said composition being greatly improved in miscibility.
2. Description of the Prior Art
A blend composition composed of a thermoplastic resin and a saponified product of ethylene-vinyl acetate copolymer (abbreviated as EVOH hereinafter) has unique characteristic properties, as disclosed in Japanese Patent Laid-open No. 20073/1981 (U.S. Pat. No. 4,284,671). It can be used in place of thermoplastic resin or EVOH in multilayer coextrusion of thermoplastic resin and EVOH, or it can be used as an interlayer between a thermoplastic resin layer and an EVOH layer to increase the interlaminar strength. The blend composition can also be made into film or sheet or bottle by melt extrusion molding, followed by stretching and/or heat treatment. These products are superior in gas barrier properties and mechanical strength. However, the blend composition is generally so poor in miscibility that it tends to undergo phase separation during extrusion molding of film, sheet, or bottle. After continued operation for a long time, the phase separation forms a foreign substance that impairs the external appearance of products. This problem also exists in the case of blend composition composed of thermoplastic resin (e.g., polyethylene terephthalate, polyamide, and polyethylene), EVOH, and ionomer, such as those disclosed in Japanese Patent Laid-open No. 141785/1977 (British Pat. No. 1545096) and Japanese Patent Laid-open No. 10149/1973 (U.S. Pat. No. 3857754 and U.S. Pat. No. 3975463).
In spite of its outstanding features, the blend composition composed of thermoplastic resin and EVOH cannot be practically used for extrusion molding or can be used only in a limited period of operation.